Ultrasonic diagnostic apparatus

ABSTRACT

A tomographic image and a tissue characteristic image that are in conformity with each other in terms of time-phase and positional relationships can be displayed superimposedly, thereby providing an excellent ultrasonic diagnostic apparatus that enables an easy and detailed observation of a relationship between a structure and a characteristic of a subject tissue. During an operation of ultrasonic wave transmission/reception (in a live mode), a control part ( 100 ) allows a tomographic image to be renewed continuously, displayed on a monitor ( 107 ), and stored in a tomographic image memory ( 110 ), while allowing an elastic modulus image as a tissue characteristic image to be renewed per heartbeat, displayed on the monitor, and stored in an elastic-modulus-image memory ( 111 ) as a tissue characteristic image memory. During a suspension of ultrasonic wave transmission/reception (in a cine mode), the control part ( 100 ) allows the elastic modulus image to be read out from the elastic-modulus-image memory and the tomographic image that is in synchronization with the elastic modulus image to be read out from the tomographic image memory, and allows these images to be displayed on the monitor.

TECHNICAL FIELD

The present invention relates to an ultrasonic diagnostic apparatus thatdisplays a superimposed tomographic image and tissue characteristicimage.

BACKGROUND ART

Conventional ultrasonic diagnostic apparatuses have a configuration inwhich the intensity of a reflection echo signal obtained as a result ofultrasonic wave irradiation onto a subject is converted into a luminanceof a corresponding pixel so that the structure of the subject isdisplayed in the form of a tomographic image. Further, in recent years,there has been an attempt to measure a movement of a subject preciselyby analyzing a phase of a reflection echo signal so as to determine anelastic modulus of the subject based on a result of the measurement.

As Conventional Example 1, a method has been proposed in whichhigh-precision tracking is performed by determining an instantaneousposition of a subject using both an amplitude and a phase of an outputsignal obtained as a result of detection of a reflection echo signal sothat minute vibrations in a large amplitude displacement motion causeddue to pulsations are captured (see, for example, JP10(1998)-005226 A).

Furthermore, as Conventional Example 2, a method and an apparatus thatare based on a development of the method according to ConventionalExample 1 have been proposed. The method is such that, with respect to alarge amplitude displacement motion of each of inner and outer surfacesof a blood vessel wall caused due to heartbeats, precise tracking fordetermining a motion speed of minute vibrations superimposed on thelarge amplitude displacement motion is performed so that a local elasticmodulus of the blood vessel wall is determined based on a difference inthe motion speed. The apparatus performs a display in such a manner thata spatial distribution of an elastic modulus is superimposed on atomographic image (see, for example, JP2000-229078 A).

However, Conventional Example 2 described above makes no mention of amethod for displaying an elastic modulus image and a tomographic imageand an operation of the apparatus. According to Conventional Example 2described above, in order to measure an elastic modulus, it is necessaryto determine an amplitude of minute vibrations by performing tracking ofa movement of a blood vessel wall caused in one heartbeat interval. Thatis, an elastic modulus image is changed only once per heartbeat. Itfollows, therefore, that since one heartbeat takes about one second, anelastic modulus image has a frame rate of about one frame per second.Meanwhile, generally, a tomographic image is displayed at 15 to 30frames per second. Thus, when a display is performed in such a mannerthat an elastic modulus image is superimposed simply on a tomographicimage, due to a large difference in frame rate, it is unclear to whichportion an elastic modulus corresponds, which has been problematic.

DISCLOSURE OF INVENTION

In view of the above-described conventional problem, it is an object ofthe present invention to provide an excellent ultrasonic diagnosticapparatus that can display a superimposed tomographic image and tissuecharacteristic image such as an elastic modulus image that are inconformity with each other in terms of time-phase and positionalrelationships during a suspension of ultrasonic wavetransmission/reception, namely, in a cine mode, thereby enabling an easyand detailed observation of a relationship between a structure and acharacteristic of a subject tissue.

In order to achieve the above-mentioned object, an ultrasonic diagnosticapparatus according to the present invention includes: ultrasonic wavetransmission/reception means that transmits/receives an ultrasonic wavewith respect to a subject; a tomographic image processing part thatforms a tomographic image representing a structure of the subject basedon a reception signal; a tissue characteristic processing part thatforms a tissue characteristic image representing a physicalcharacteristic of a tissue of the subject through analysis of thereception signal; memory means (tomographic image memory, tissuecharacteristic image memory) that stores the tomographic image and thetissue characteristic image, respectively; an image composing part thatcombines at least the tomographic image and the tissue characteristicimage; display means that displays at least the tomographic image andthe tissue characteristic image; and control means that, during anoperation of ultrasonic wave transmission/reception (in a live mode),allows the tomographic image to be renewed in an arbitrary cycle,displayed by the display means, and stored in the memory means, whileallowing the tissue characteristic image to be renewed in a cycledifferent from the cycle for the tomographic image, displayed by thedisplay means, and stored in the memory means, and during a suspensionof ultrasonic wave transmission/reception (in a cine mode), allowsarbitrary one of the tissue characteristic images that have beenacquired previously and one of the tomographic images that is insynchronization with the tissue characteristic image to be read out fromthe memory means, respectively and displayed by the display means.

According to this configuration, in a live mode, a tomographic image canbe obtained in real time, and thus a probe operation such as forpositioning and operations of setting various values such as a gain canbe performed easily, and in a cine mode, a tomographic image and atissue characteristic image can be obtained that are in conformity witheach other in terms of time-phase and positional relationships between astructure and a characteristic of a subject tissue.

In the ultrasonic diagnostic apparatus configured as above, preferably,the display means is divided into a first display region and a seconddisplay region, and displays at least the tomographic image in the firstdisplay region and at least the tomographic image on which the tissuecharacteristic image is superimposed in the second display region.During the operation of ultrasonic wave transmission/reception, thecontrol means allows the tomographic image to be displayed at least inthe first display region of the display means, while allowing the tissuecharacteristic image to be displayed in the second display region of thedisplay means, and during the suspension of ultrasonic wavetransmission/reception, the control means allows the tissuecharacteristic image and one of the tomographic images that is insynchronization with the tissue characteristic image to be read out fromthe memory means, respectively and displayed at least in the seconddisplay region of the display means.

According to this configuration, a display screen is divided into two,and thus a portion hidden by a tissue characteristic image also can beviewed at the same time. Therefore, in a live mode, a probe operationsuch as for positioning and operations of setting various values such asa gain can be performed more easily. Further, in a cine mode, atomographic image and a tissue characteristic image that coincide witheach other in time phase can be obtained at the same time, and thus bycomparing the tomographic image with the tissue characteristic image, arelationship between a structure and a characteristic of a subjecttissue can be grasped easily.

Furthermore, preferably, during the operation of ultrasonic wavetransmission/reception, one of the tomographic images that is insynchronization with the tissue characteristic image is displayed in thesecond display region. According to this configuration, even in a livemode, a tomographic image and a tissue characteristic image that are inconformity with each other in terms of a positional relationship betweena structure and a characteristic of a subject tissue are displayed in asecond display region, thereby allowing a diagnosis result to beobtained immediately.

Furthermore, preferably, during the suspension of ultrasonic wavetransmission/reception, one of the tomographic images that is insynchronization with the tissue characteristic image is displayed in thefirst display region. According to this configuration, in a cine mode, atomographic image and a tissue characteristic image that coincide witheach other in time phase can be obtained at the same time, and thus bycomparing the tomographic image with the tissue characteristic image, arelationship between a structure and a characteristic of a subjecttissue can be grasped easily.

Furthermore, preferably, during the suspension of ultrasonic wavetransmission/reception, the tissue characteristic image that is obtainedbased on a time period in which the tomographic image displayed in thefirst display region is included and the tomographic image that is insynchronization with the tissue characteristic image are displayedsuperimposedly in the second display region. According to thisconfiguration, a tomographic image can be displayed frame by frame in afirst display region, thereby allowing a detailed examination of adynamic structural change of a subject tissue in a time period used forcalculation of a characteristic of the tissue.

Furthermore, preferably, the image composing part allows a relatedwaveform that contains information corresponding to at least one of thetomographic image and the tissue characteristic image to be displayed ona display screen of the display means in such a manner as to be combinedwith the tomographic image and the tissue characteristic image, andduring the suspension of ultrasonic wave transmission/reception, thecontrol means allows a portion of the related waveform to be displayedin a highlighted manner, which corresponds to a time period in which thetissue characteristic image being displayed is formed. According to thisconfiguration, it is possible to establish a visual correspondencebetween a tissue characteristic image and a portion of anelectrocardiographic waveform or a phonocardiographic waveform thatcorresponds to a time period in which the tissue characteristic image isformed.

Furthermore, preferably, a tissue characteristic is an elastic modulus.According to this configuration, an elastic modulus image can beobtained that represents hardness/softness of a subject tissue and is inconformity in terms of a positional relationship with a tomographicimage representing a structure of the tissue.

As an alternative, preferably, a tissue characteristic is a strain or astrain rate. According to this configuration, a characteristic of asubject tissue can be shown excellently that represents deformability ofthe tissue and is in conformity in terms of a positional relationshipwith a tomographic image representing a structure of the tissue.

As an alternative, preferably, a tissue characteristic is a viscosity.According to this configuration, a characteristic of a subject tissuecan be shown excellently that represents a viscosity of the tissue andis in conformity in terms of a positional relationship with atomographic image representing a structure of the tissue.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing an example of a configuration of anultrasonic diagnostic apparatus according to each of embodiments of thepresent invention.

FIG. 2 is a timing chart showing an electrocardiographic orphonocardiographic waveform, tomographic image display frames,elastic-modulus-image display frames according to Embodiment 1 of thepresent invention.

FIG. 3 is a diagram showing an example of a monitor display screen in alive mode illustrated in FIG. 2.

FIG. 4 is a diagram showing an example of a monitor display screen rightafter being frozen as illustrated in FIG. 2.

FIG. 5 is a diagram showing an example of a monitor display screen in acine mode illustrated in FIG. 2.

FIG. 6 is a diagram showing an example of a monitor display screenaccording to a modification of Embodiment 1 of the present invention.

FIG. 7 is a diagram showing an example of a monitor display screen in alive mode in an ultrasonic diagnostic apparatus according to Embodiment2 of the present invention.

FIG. 8 is a diagram showing an example of a monitor display screen in acine mode in the ultrasonic diagnostic apparatus according to Embodiment2 of the present invention.

FIG. 9 is a timing chart showing an electrocardiographic orphonocardiographic waveform, left-side tomographic image display frames,right-side tomographic image display frames, and elastic-modulus-imagedisplay frames according to Embodiment 2 of the present invention.

FIG. 10 is a timing chart showing an electrocardiographic orphonocardiographic waveform, left-side tomographic image display frames,right-side tomographic image display frames, and elastic-modulus-imagedisplay frames according to a modification of Embodiment 2 of thepresent invention.

FIG. 11 is a timing chart showing an electrocardiographic orphonocardiographic waveform, left-side tomographic image display frames,right-side tomographic image display frames, and elastic-modulus-imagedisplay frames according to another modification of Embodiment 2 of thepresent invention.

FIG. 12 is a timing chart showing an electrocardiographic orphonocardiographic waveform, left-side tomographic image display frames,right-side tomographic image display frames, and elastic-modulus-imagedisplay frames according to still another modification of Embodiment 2of the present invention.

FIG. 13 is a diagram showing an example of a monitor display screen in acine mode illustrated in FIG. 11 or FIG. 12.

DESCRIPTION OF THE INVENTION

Hereinafter, the present invention will be described by way of preferredembodiments with reference to the appended drawings.

In each of the embodiments of the present invention, the description isdirected to the case in which a tissue characteristic image is anelastic modulus image. However, the present invention is not limitedthereto and is applicable to any tissue characteristic image of asubject tissue that is acquired in a cycle different from a cycle for atomographic image such as an image representing a strain, a strain rate,a viscosity or the like of a tissue.

Embodiment 1

FIG. 1 is a block diagram showing an example of a configuration of anultrasonic diagnostic apparatus according to Embodiment 1 of the presentinvention. In FIG. 1, a control part 100 as control means controlsoperations of the entire ultrasonic diagnostic apparatus. This controlrelates to all operations such as setting of various parameters forsignal processing, control of transmission/reception timing, live/cinemode switching by pressing of a freeze key, mode control, and control ofa screen display.

Upon reception of an instruction from the control part 100, atransmission part 102 drives a probe 101. The probe 101 converts atransmission drive signal from the transmission part 102 into anultrasonic wave and irradiates the ultrasonic wave to a subject, whileconverting an ultrasonic echo reflected from inside the subject into anelectric signal. A reception part 103 amplifies a reception signal,while detecting only an ultrasonic wave from a predeterminedposition/direction.

A tomographic image processing part 104 is composed of a bandpassfilter, a logarithmic amplifier, a wave detector and the like and formsan image representing an internal structure of the subject. Generally, atomographic image is formed at 15 to 30 frames per second. In thisembodiment, an elastic modulus is used as a tissue characteristicrepresenting a physical characteristic of a tissue. Accordingly, anelastic-modulus-image processing part 105 that is a tissuecharacteristic image processing part measures, based on a receptionsignal, a strain of a subject tissue caused due to a change in bloodpressure, calculates a local elastic modulus of the tissue based on adifference in blood pressure measured in a blood pressure measuring part108 and the strain, and forms an image representing a result of thecalculation. In this embodiment, an elastic modulus is calculated byusing, for example, the algorithm disclosed in Conventional Example 2.That is, a movement of the tissue caused in one heartbeat interval istracked so that a strain of the tissue is determined, and an elasticmodulus is calculated based on a maximum blood pressure and a minimumblood pressure that occur in one heartbeat interval. That is, an elasticmodulus image is formed once per heartbeat.

An image composing part 106 combines a tomographic image formed in thetomographic image processing part 104, an elastic modulus image formedin the elastic-modulus-image processing part 105, and anelectrocardiographic waveform or a phonocardiographic waveform obtainedin an electrocardiographic or phonocardiographic measurement part 109,allowing these combined images to be displayed on a monitor 107 asdisplay means. Further, a tomographic image memory 110 and anelastic-modulus-image memory 111 as memory means store a tomographicimage and an elastic modulus image, respectively, and a waveform memory112 stores a phonocardiographic waveform or an electrocardiographicwaveform.

The following describes an operation of the ultrasonic diagnosticapparatus having the above-described configuration in further detailwith reference to FIGS. 2 to 5.

FIG. 2 is a timing chart showing an electrocardiographic waveform 204,display frames of a tomographic image 200, and display frames of anelastic modulus image 201, which are displayed on the monitor 107 in astate where data is changed during an operation of ultrasonic wavetransmission/reception (hereinafter, referred to as a live mode) and astate where previous data is referred to during a suspension ofultrasonic wave transmission/reception (hereinafter, referred to as acine mode).

FIG. 3 shows a display screen of the monitor 107 in the live mode shownin FIG. 2. FIG. 4 shows a display screen of the monitor 107 right afterbeing shifted to the cine mode by pressing of a freeze key. FIG. 5 showsa display screen of the monitor 107 in the case where an image reversingoperation is performed in the cine mode shown in FIG. 2.

As shown in each of FIGS. 3 to 5, on a display screen of the monitor107, the elastic modulus image 201 is displayed in such a manner as tobe superimposed on the tomographic image 200. Further, on the displayscreen, a reflection intensity scale 202 that shows a correspondencebetween an reflection intensity of the tomographic image 200 and aluminance on the screen, an elastic modulus scale 203 that shows acorrespondence between an elastic modulus and a color tone or aluminance on the screen, an electrocardiographic or phonocardiographicimage 204, and the like are displayed. As an example, the tomographicimage 200 and the elastic modulus image 201 shown in each of FIGS. 3 to5 show across section along a longitudinal axis of a blood vessel (bloodvessel wall 301) having an atheroma 302.

The following description is made in accordance with the timing shown inFIG. 2.

Firstly, in the live mode, the tomographic image 200 is changedcontinuously at 15 to 30 frames per second so that a newest image isdisplayed at all times. Meanwhile, the elastic modulus image 201 to bedisplayed in such a manner as to be superimposed on the tomographicimage 200 is formed by calculation of an elastic modulus based on astrain of a tissue and a difference in blood pressure that are caused inone heartbeat interval, and thus is changed in synchronization with aheartbeat, so that the elastic modulus image 201 obtained in a heartbeatperiod preceding by one heartbeat interval is displayed. Although thetomographic image 200 that is in correspondence with the elastic modulusimage 201 in terms of time-phase and positional relationships(hereinafter, expressed as being “in synchronization”) is one of imagesobtained in one heartbeat period, an initial tomographic image isassumed to be used herein.

That is, referring to FIG. 2, a elastic-modulus-image display frame C isformed using an elastic modulus calculated based on a reception signalobtained in a heartbeat period c, and thus only a tomographic imagedisplay frame 2 that is obtained initially in the heartbeat period c isin synchronization with the elastic-modulus-image display frame C.Consequently, in the live mode, there is no coincidence between anelastic modulus represented by the elastic modulus image 201 and atissue structure represented by the tomographic image 200.

In the live mode, the tomographic image 200 and the elastic modulusimage 201 are stored in the tomographic image memory 110 and the elasticmodulus memory 111, respectively. Further, a phonocardiographic orelectrocardiographic waveform obtained in the electrocardiographic orphonocardiographic measurement part 109 is displayed continuously on thescreen and stored in the waveform memory 112.

Next, right after a shift to the cine mode is performed in whichultrasonic wave transmission/reception is suspended by pressing of thefreeze key, as shown in FIG. 4, a newest image as the elastic modulusimage 201 and one of the tomographic images 200 that is insynchronization with the newest image are displayed on the monitor 107.Referring to FIG. 2, a display frame D (denoted by 201(D)) of the newestimage as the elastic modulus image 201 at a point of time when thefreeze key is pressed, is an elastic modulus image formed based on astrain caused in a heartbeat period d. Therefore, a display frame 7(200(7)) of a tomographic image as the tomograhic image 200 that isobtained initially in the heartbeat period d and is in synchronizationwith the frame D is read out from the tomographic image memory 110 andis displayed on the monitor 107. Further, as shown in FIG. 4, a portionof the electrocardiographic or phonocardiographic waveform 204 thatcorresponds to a heartbeat period CC (=d) in which theelastic-modulus-image display frame 201(D) is formed is displayed in ahighlighted manner by means of a change in luminance or color tone(shown by a bold line in the figure).

In the cine mode, it is possible to refer to a previous image byperforming an image reversing/forwarding operation. In this embodiment,only an elastic-modulus-image display frame and a tomographic imagedisplay frame that is in synchronization therewith are read out from theelastic-modulus-image memory 111 and the tomographic image memory 110,respectively, and are displayed. Referring to FIG. 2, when an imagereversing operation is performed, the immediately preceding displayframe C (201(C)) of the elastic modulus image 201 is read out from theelastic-modulus-image memory 111, while the display frame 2 (200(2)) ofthe tomographic image 200 that is in synchronization with theelastic-modulus-image display frame 201(C) is read out from thetomographic image memory 110, and these frames are displayed.

As shown in FIG. 5, the elastic-modulus-image display frame 201(C) andthe tomographic image display frame 200(2) are displayed assuperimposed, and a portion of the electrocardiographic orphonocardiographic waveform 204 that corresponds to a heartbeat periodCC (=c) in which an elastic modulus image being displayed is formed isdisplayed in a highlighted manner by means of a change in luminance orcolor tone (shown by a bold line in the figure).

Referring to FIG. 2, when an image forwarding operation is performedsubsequently, the elastic-modulus-image display frame D that immediatelyfollows the elastic-modulus-image display frame C is read out from theelastic-modulus-image memory 111, while the tomographic image displayframe 7 that is in synchronization with the elastic-modulus-imagedisplay frame D is read out from the tomographic image memory 110, andthese frames are displayed on the monitor 107.

As described above, according to this embodiment, in a live mode, atomographic image can be obtained in real time, and thus a probeoperation such as for positioning and operations of setting variousvalues such as a gain can be performed easily, and in a cine mode, atomographic image and an elastic modulus image can be obtained that arein conformity with each other in terms of time-phase and positionalrelationships between a structure and an elastic modulus of a subjecttissue.

By enabling ON/OFF switching between superimposed and non-superimposedstates of the elastic modulus image 201 on the tomographic image 200,the relationship between an elastic modulus and a structure can begrasped more easily.

Moreover, the same effect also can be obtained by, as shown in FIG. 6,displaying only a region (ROI: Region of Interest) 208 to be examined onthe tomographic image 200 using a broken line, and displaying an imageas the elastic modulus image 201 that corresponds to the ROI 208 in aseparate region.

Embodiment 2

The following describes an ultrasonic diagnostic apparatus according toEmbodiment 2 of the present invention. The ultrasonic diagnosticapparatus according to this embodiment has the same configuration asshown in FIG. 1 referred to in the description of Embodiment 1. Adifference from Embodiment 1 is that a display screen of a monitor 107is divided into two, and only a tomographic image is displayed in onedisplay region (left-side display region), and a tomographic image onwhich an elastic modulus image 201 is superimposed is displayed in theother display region (right-side display region).

FIG. 7 shows a display screen of the monitor 107 in a live mode, andFIG. 8 shows a display screen of the monitor 107 in the case where animage reversing operation is performed in a cine mode. FIG. 9 is atiming chart showing an electrocardiographic or phonocardiographicwaveform 204, display frames of a left-side tomographic image 205 onwhich an elastic modulus image 201 is not superimposed, display framesof a right-side tomographic image 206 on which the elastic modulus image201 is superimposed, and display frames of the elastic modulus image201, which are displayed on the monitor 107 in the live mode and thecine mode.

In FIG. 9, as for the right-side tomographic image 206 on which theelastic modulus image 201 is superimposed, the same applies as inEmbodiment 1. Meanwhile, in the cine mode, the display frames of theleft-side tomographic image 205 are in synchronization with the displayframes of the elastic modulus image 201.

As described above, a display screen is divided into two, and thus aportion hidden by the elastic modulus image 201 also can be viewed atthe same time. Therefore, in the live mode, a probe operation such asfor positioning and operations of setting various values such as a gaincan be performed more easily. Further, in the cine mode, a tomographicimage and a elastic modulus image that coincide with each other in timephase can be obtained at the same time, and thus by comparing thetomographic image with the elastic modulus image, the relationshipbetween a structure and an elastic modulus of a subject tissue can begrasped easily.

FIG. 10 is a timing chart showing the electrocardiographic orphonocardiographic waveform 204, display frames of the left-sidetomographic image 205 on which the elastic modulus image 201 is notsuperimposed, display frames of the right-side tomographic image 206 onwhich the elastic modulus image 201 is superimposed, and display framesof the elastic modulus image 201, which are displayed on the monitor 107in the live mode and the cine mode, according to a modification of thisembodiment.

Referring to FIG. 10, even in the live mode, a display frame 2 of theright-side tomographic image 206 is in synchronization with a displayframe C of the elastic modulus image 201. An operation performed in thecine mode is the same as in the case shown in FIG. 9.

As described above, according to the modification of this embodiment,even in a live mode, a tomographic image and the elastic modulus image201 that are in conformity with each other in terms of a positionalrelationship between a structure and an elastic modulus of a subjecttissue are displayed in the right-side display region for the right-sidetomographic image 206, thereby allowing a diagnosis result to beobtained immediately.

Each of FIGS. 11 and 12 is a timing chart showing theelectrocardiographic or phonocardiographic waveform 204, display framesof the left-side tomographic image 205 on which the elastic modulusimage 201 is not superimposed, display frames of the right-sidetomographic image 206 on which the elastic modulus image 201 issuperimposed, and display frames of the elastic modulus image 201, whichare displayed on the monitor 107 in the live mode and the cine mode,according to each of other modifications of this embodiment. Operationsin the live mode shown in FIGS. 11 and 12 are the same as those shown inFIGS. 9 and 10, respectively. The following mainly describes thedifferences.

Firstly, right after a shift to the cine mode is performed by pressingof a freeze key, referring to FIG. 11 or FIG. 12, in the right-sidedisplay region for the right-side tomographic image 206, a display frameD of a newest elastic modulus image and a display frame 7 of atomographic image that corresponds thereto are displayed, while in theleft-side display region for the left-side tomographic image 205, adisplay frame 13 of a newest tomographic image is displayed.

Next, when an image reversing operation is performed in the cine mode,in the left-side display region for the left-side tomographic image 205,an immediately preceding frame as a tomographic image is displayedsequentially by reading out from a tomographic image memory 110 (displayframes 12, 11, 10, . . . ). Meanwhile, in the right-side display regionfor the right-side tomographic image 206, an elastic-modulus-imagedisplay frame 201(D) that is obtained based on a heartbeat period inwhich a frame being displayed as the left-side tomographic image 205 isincluded is displayed by reading out from an elastic-modulus-imagememory 111, while a tomographic image display frame 206(7) that is insynchronization with the elastic-modulus-image display frame 201(D) isdisplayed by reading out from the tomographic image memory 110.

In this case, however, since a heartbeat period including the image atthe timing when the freeze key is pressed is not completed, anelastic-modulus-image display frame obtained right before the heartbeatperiod and a tomographic image display frame corresponding thereto aredisplayed.

Thus, according to either of operations shown in FIGS. 11 and 12, everytime an image reversing operation is performed, in the left-side displayregion for the left-side tomographic image 205, an immediately precedingframe as a tomographic image is displayed sequentially by reading outfrom the tomographic image memory 110. Meanwhile, in the right-sidedisplay region for the right-side tomographic image 206, only after aheartbeat period in which the left-side tomographic image 205 isincluded is shifted from d to c, that is, the left-side tomographicimage 205 is changed from a display frame 7 to a display frame 6 and isdisplayed, the elastic-modulus-image display frame 201(D) and thetomographic image display frame 206(7) corresponding thereto are changedto an elastic-modulus-image display frame 201(C) and a tomographic image206(2) corresponding thereto, respectively, and are displayed.

FIG. 13 shows a display screen in the case where, as a result ofperforming an image reversing operation illustrated in FIG. 11 or FIG.12, a change to the elastic-modulus-image display frame 201(C) and thetomographic image display frame 206(2) corresponding thereto isperformed. In the left-side display region for the left-side tomographicimage 205, a tomographic image display frame 205(5) is displayed, whilein the right-side display region for the right-side tomographic image206, the superimposed elastic-modulus-image display frame 201(C) andtomographic image display frame 206(2) are displayed. Further, a portionof the electrocardiographic waveform or phonocardiographic waveform 204that corresponds to a heartbeat period in which an elastic modulus imagebeing displayed is formed is displayed in a highlighted manner by meansof a change in luminance or color tone (shown by a bold line in thefigure), and a maker 207 that indicates a time phase of the displayframe 205(5) of the left-side tomographic image 205 is displayed belowthe waveform.

As described above, according to the other modifications of thisembodiment, in a left-side display region for the left-side tomographicimage 205, a tomographic image can be displayed frame by frame, therebyallowing a detailed examination of a dynamic structural change of asubject tissue in a heartbeat period used for a calculation of anelastic modulus.

Similarly to Embodiment 1, by enabling ON/OFF switching betweensuperimposed and non-superimposed states of the elastic modulus image201 on the right-side tomographic image 206, a relationship between anelastic modulus and a structure can be grasped more easily.

Each of the embodiments of the present invention describes an ultrasonicdiagnostic apparatus that calculates a strain of a subject tissueresponsive to a change in blood pressure per heartbeat so as todetermine an elastic modulus. However, the present invention also isapplicable to an ultrasonic diagnostic apparatus that determines tissuecharacteristics of a subject such as a strain, a strain rate, an elasticmodulus, a viscosity and the like of the tissue by calculation based ona change caused in a reception signal due to externally causedcompression/relaxation or vibrations. In this case, preferably, aformation cycle of a tissue characteristic image is set so as tocoincide with a cycle of the occurrence of the externally causedcompression/relaxation or vibrations.

Furthermore, a one-dimensional waveform displayed on the display screenof the monitor 107 is not limited to an electrocardiographic or aphonocardiographic waveform. Various types of related waveforms can bedisplayed that include a waveform representing information on a subjectsuch as a waveform of a blood pressure measured in real time and awaveform showing a change in internal diameter of a blood vessel, atissue tracking waveform and a waveform showing a change in thickness ofa tissue, and a waveform representing a progress in determining anelastic modulus such as a waveform showing a strain. Thus, in the casewhere a waveform representing information on a subject is displayed, itis possible to obtain the necessary information on the subject from onescreen without referring to a separate display apparatus. Further, inthe case where a waveform representing a progress is displayed, it ispossible to perform a detailed observation of information used forconclusive determination of a tissue characteristic. That is, byallowing a waveform to be displayed that contains informationcorresponding to at least one of a tomographic image and a tissuecharacteristic image, effective referring to information related to animage being displayed is enabled. Moreover, a time period in which anelastic modulus image is formed can be displayed in a highlighted mannerby various methods without any limitation to the use of a change inluminance or color tone. Such methods include the use of a differenttype of line such as a bold line, a thin line, a dotted line or the likeand the enclosure with a square, parentheses or the like. Thus,information on a waveform corresponding to a time period in which anelastic modulus image is formed can be recognized at a glance.

INDUSTRIAL APPLICABILITY

According to the present invention, a tomographic image and a tissuecharacteristic image that are in conformity with each other in terms oftime-phase and positional relationships can be displayed superimposedly,and thus an excellent ultrasonic diagnostic apparatus can be providedthat enables an easy and detailed observation of a relationship betweena structure and a characteristic of a subject tissue.

1. An ultrasonic diagnostic apparatus, comprising: ultrasonic wavetransmission/reception means that transmits/receives an ultrasonic wavewith respect to a subject; a tomographic image processing part thatforms a tomographic image representing a structure of the subject basedon a reception signal; a tissue characteristic image processing partthat forms a tissue characteristic image representing a physicalcharacteristic of a tissue of the subject through analysis of thereception signal of plural frames including at least one contractionand/or expansion period of the tissue; memory means that stores thetomographic image and the tissue characteristic image, respectively; animage composing part that combines at least the tomographic image andthe tissue characteristic image; display means that displays at leastthe tomographic image and the tissue characteristic image; and controlmeans for controlling an operation of the ultrasonic wavetransmission/reception means, the tomographic image processing part, thetissue characteristic image processing part, the memory means, the imagecomposing part and the display means, wherein during an operation of theultrasonic wave transmission/reception means, the control means isconfigured to allow the tomographic image to be renewed in an arbitrarycycle, displayed by the display means, and stored in the memory means,while allowing the tissue characteristic image to be renewed in a cycledifferent from the cycle for the tomographic image and corresponding toat least one contraction and/or expansion period of the tissue, allowingthe tissue characteristic image obtained for a period at least one cyclebefore to be displayed by the display means, and allowing the tissuecharacteristic image to be stored in the memory means, and during asuspension of the ultrasonic wave transmission/reception means, thecontrol means is configured to allow an arbitrary one of the tissuecharacteristic images that have been acquired previously and one of thetomographic images that is in synchronization with the tissuecharacteristic image to be read out from the memory means, respectivelyand displayed by the display means.
 2. The ultrasonic diagnosticapparatus according to claim 1, wherein the display means is dividedinto a first display region and a second display region, and displays atleast the tomographic image in the first display region and at least thetomographic image on which the tissue characteristic image issuperimposed in the second display region, during the operation of theultrasonic wave transmission/reception means, the control means isconfigured to allow the tomographic image to be displayed at least inthe first display region of the display means, while allowing the tissuecharacteristic image to be displayed in the second display region of thedisplay means, and during the suspension of the ultrasonic wavetransmission/reception means, the control means is configured to allowthe tissue characteristic image and one of the tomographic images thatis in synchronization with the tissue characteristic image to be readout from the memory means, respectively and displayed at least in thesecond display region of the display means.
 3. The ultrasonic diagnosticapparatus according to claim 2, wherein during the operation ofultrasonic wave transmission/reception, one of the tomographic imagesthat is in synchronization with the tissue characteristic image isdisplayed in the second display region.
 4. The ultrasonic diagnosticapparatus according to claim 2, wherein during the suspension ofultrasonic wave transmission/reception, one of the tomographic imagesthat is in synchronization with the tissue characteristic image isdisplayed in the first display region.
 5. The ultrasonic diagnosticapparatus according to claim 2, wherein during the suspension ofultrasonic wave transmission/reception, the tissue characteristic imagethat is obtained based on a time period in which the tomographic imagedisplayed in the first display region is included and the tomographicimage that is in synchronization with the tissue characteristic imageare displayed superimposedly in the second display region.
 6. Theultrasonic diagnostic apparatus according to claim 1, wherein the imagecomposing part allows a related waveform that contains informationcorresponding to at least one of the tomographic image and the tissuecharacteristic image to be displayed on a display screen of the displaymeans in such a manner as to be combined with the tomographic image andthe tissue characteristic image, and during the suspension of ultrasonicwave transmission/reception, the control means allows a portion of therelated waveform to be displayed in a highlighted manner, whichcorresponds to a time period in which the tissue characteristic imagebeing displayed is formed.
 7. The ultrasonic diagnostic apparatusaccording to claim 1, wherein the tissue characteristic image is anelastic modulus image.
 8. The ultrasonic diagnostic apparatus accordingto claim 1, wherein the tissue characteristic image is an imagerepresenting a strain or a strain rate.
 9. The ultrasonic diagnosticapparatus according to claim 1, wherein the tissue characteristic imageis an image representing a viscosity.